Polyphenylene ether is known as an engineering plastic having high flame retardancy, heat resistance, dimensional stability, non-moisture-absorbing properties and electrical properties, but has demerits such as poor melting fluidity and inferior moldability and impact resistance. For this reason, often, polyphenylene ether is mixed with other polymer and used to take advantages of polyphenylene ether and compensate for its demerits. Examples of the other polymer include block copolymers of a hydrogenated styrene and a conjugated diene (hereinafter, also referred to as a “hydrogenated block copolymer”) and various polymers such as polypropylene-based resins.
The hydrogenated block copolymers have high thermal stability and weatherability while these copolymers have demerits. For example, rubber elasticity at a high temperature is insufficient, leading to large deformation due to heat and pressure, and large compression set at a high temperature.
Moreover, the polypropylene-based resin is an inexpensive plastic having low specific gravity, and has high resistance against chemicals, solvent resistance, moldability, and the like. For this reason, the polypropylene resin is used in various fields of automobile parts, electrical and electronic parts, household electrical appliance parts, and the like.
In order to provide merits of these polyphenylene ether, hydrogenated block copolymers, and polypropylene resins and compensate for their demerits, a variety of resin compositions prepared by using these components in combination properly and mixing the components have been proposed.
For example, Patent Literatures 1 to 4 propose polyphenylene ether resin/hydrogenated block copolymer compositions, and Patent Literatures 5 to 14 propose polyphenylene ether/polypropylene-based resin compositions. In the case where high fluidity is required in the resin composition as above in which the polyphenylene ether resin and the polypropylene resin are blended, it apparently can be expected that the processability of the resin composition to be obtained is improved by reducing the molecular weight of polyphenylene ether as a factor to determine the fluidity of polyphenylene ether.
Moreover, production methods enabling processing using general-purpose process machines and conditions in the case where the resin composition containing polyphenylene ether is obtained have been proposed. For example, Patent Literatures 15 and 16 describe resin compositions containing polyphenylene ether and polystyrene and the production methods thereof.